Machining Of Rotating Surface Of B₄C Ceramics By Wire Electrical Discharge Machining

With the development of engineering, the engineering material which is usedto the engineering application put forward the new request. The traditional metalmaterials have already been more incompetent for the demand of the engineeringapplication. but the advanced ceramics have many good properties that metalsdon't have, such as the high hardness, high strength, high wearable and heat-resistant,acid-proofand alkali-proof,lowdensity,coefficient of low hot expansionand coefficient of Coefficient of low heat conduction, So there is a broadapplication prospect in the fields of industry, such as machinery, space flight,national defense, and becoming one of the modern engineering materials pillarsgradually.Although the advancedceramics have so manygood properties, but anvancedceramics that are got through fritting are different from metal powder products,shrinking rate of its size is above 10%, and the latter is in under 0.2%, so the sizeof the ceramics are low in precision, can't serve as machine components directly,must undergo fine machining, and ceramics are the typical hard-fragile materials,the traditionalmachiningmethodisverydifficulttobecompetent.At present, the machining method of advanced ceramics have diamondgrinding, ultra hard cutters such as PCD, ultrasonic cutting , laser cutting , plasmaarccuttingandwater-jetcutting.Buttheyallhavetheir shortcomings.It is obvious advanced ceramics difficult to machine is the main factor thatrestricttheirapplication,especiallyithasadifficultproblemtomachineitsrotatingsurface and special-shaped ,people have been exploring a kind of valid means ofmachiningadvancedceramics.Wire Electrical Discharge Grinding is a effective means which is applied tomachine micro-shafts , it is basically identical that its mechanism to WEDM inessence, WEDM( wire electrical discharge machining,),is one of the specialmethods that has beenusedextensivelytomachinemetal,it is abreak-through thatuse the soft metal material to machine the hard material, and it is a non-contactmachining technique with little cutting force between work piece and electrode,sothe product will not be fracture during the processing duo to thestress(shear stressmainly),ortheresidual stressgreatlytoreduceproductproperties aftermachining,so it is a kind of ideal means to machining advanced ceramics. The experimentprove, WEDMcan be used to machineif the product electrical resistance lessthan100Ω·cm(conductivityis greaterthan0.01s/cm ) . However,the WEDGequipmentused in domestic and international laboratory can not be extensive applicationbecauseoftheirhighprice.This paper put forward a process which based on high-speed WEDMmachining rotating surface of advanced ceramics by WEDG , it has the followtraits, control easy, numerical control, high performance, low price. Through thetransformation of the machine tool, we can machine the rotating surface ofadvancedceramicssuccessfully.Based on the elaboration of the current situation and the characteristics of thetechnologyoflasercutting,ultrasoniccutting,abrasivewater-jetcutting,plasmaarc cutting and for the machining of rotating surface of advanced ceramics byWEDM , transforming the machine tool, manufacturing the rotating system, wholesystem has realized good electric conductivity and stability. Through figureoscillograph we survey the discharge interval voltage state, compare metal andceramics discharge waveform difference, and analyzethe reason for causingthedifference. Through the experimental analysis of the single factor we survey theinfluenceoftheparametertotheworkpiecesurfacequality,thesinglepulseenergyis a main factor of influencing the surface roughness of the work piece, thealternate of the pulse influences the stability of the processing course directly.Through scan electric mirror we observe the surface of B4C before machining andafter machining and the surface of metal after machining, and machiningmechanismhas beenanalyzed ,proposethemicroshape ofthe surfaceofadvancedceramics after electric machining is more complicated than the metal material, thedifferencearemanykindsofmachiningmechanisminfluence the resultof functiontogether. Processing the special-shaped and axial symmetry of B4C by the rotatingsystem,haveexpandedtheprocessingrangeofthewholesystem.The experiment prove thethesis "WEDG with theory, WEDM with platform" is a feasible method to machine the rotating surface of advanced ceramics, andwhole system have low cost, apt to realize numerical control ,can machine axialsymmetryproduct,itisamoreidealprocessingandhaveabrightfuture.